Traditionally, pushrim propulsion has been used in powering a wheelchair. Pushrims are provided adjacent to the main wheels of the wheelchair, allowing a person to apply force to the pushrims in order to move the wheelchair forwardly or rearwardly. A concern with the use of pushrim propulsion is that the poor human-to-chair biomechanics result in inefficiencies, and sometimes injury. Users of pushrim wheelchairs may suffer from Repetitive Strain Injuries (RSI) of the wrist and shoulders.
As an alternative to pushrim propulsion, other approaches for manually driving wheelchairs include the use of levers which are “rowed” and the use of handcycles which are “peddled.” Such approaches avoid some of the ergonomic and inefficiency shortcomings of pushrim propulsion.
As an alternative to manual wheelchairs for users with limited dexterity and strength, electric wheelchairs are increasing in popularity. Electric wheelchairs include one or more motors attached to drive wheels for control by the wheelchair user. A joystick may be located for easy access by the user to dictate forward and rearward movement, as well as steering. A battery is carried by the wheelchair for providing power to each motor. Particularly for the aged, electric wheelchairs significantly increase mobility.
The transportation of wheelchairs presents a considerable challenge. The battery and motors of an electric wheelchair increase the weight and the volume concerns. Vehicles may be adapted specifically for transporting wheelchairs, such as carrier vans and lifts. However, such vehicles are not always available. Moreover, the transportation challenges remain for public transportation, such as the use of buses, trains, and airplanes. Air travel requires that the size and weight of the wheelchair remain manageable. Often, manual wheelchairs are designed to be folded. Reducing the size of an electric wheelchair is more problematic.
One method of addressing the transportation challenge is to construct the wheelchair as a number of interconnecting modules that can be assembled and disassembled as needed. U.S. Pat. No. 6,220,382 to Kramer, Jr. et al. describes a powered wheelchair with a separate center frame. The center frame includes a center bar and components welded to the bar, including a support for a battery and a crossbar to which a pair of threaded knobs are attached. The threaded knobs are used to secure a drive assembly in position along the bar after the bar has been passed through a tube of the drive assembly for attachment with a footrest. Two rear stabilizing wheels are attached to the end of the bar opposite to the footrest.
While prior art techniques for forming modular wheelchairs operate well in allowing users to readily disassemble the chair, further advances are available, particularly in the areas of reducing the difficulty of disassembly and enabling a more compact and readily carried disassembly of modules.